Maskless EUV lithography, an alternative to e-beam

Abstract. Background: The resolution capability of EUV lithography has reached parity with e-beam, raising the possibility that maskless EUV could supplant e-beam for mask writing and low-volume wafer patterning. Aim: We outline a maskless EUV scanner design with a 13.5-nm operating wavelength and numerical aperture of 0.55. Approach: A microlens array partitions radiation from a commercial laser-produced plasma EUV source into ∼2 million individual beams, which are focused to separate, diffraction-limited focal points on a writing surface, and the surface is raster-scanned across the focal point array as the beams are individually modulated by MEMS microshutters integrated within the microlens array to construct a digitally synthesized raster exposure image. Results: Compared to state-of-the-art mask-projection EUV lithography, the system would have ∼1000  ×   lower throughput, but its power requirement would also be ∼1000  ×   lower, the exposure dose would be ∼10  ×   higher, scan velocity and acceleration would be ∼1000  ×   lower, and it would have the advantage of maskless operation. In comparison to e-beam mask writers, a maskless EUV scanner could provide higher resolution with at least double the throughput and over 10  ×   higher dose. Conclusions: Maskless EUV lithography could provide significant cost and performance benefits for both direct-write applications and photomask production for mask-projection lithography.